Optical fiber as used in standard telecommunications and other applications is based upon the principles of Snell's Law and total internal reflection. Each fiber is made up of a central core and an outer layer known as the cladding. By establishing a core with an index of refraction (n) higher that the index of refraction of the cladding, the light will totally reflect internally rather than passing through the core and being lost.
Optical fiber connectors are made possible through the employment of a device known as a ferrule. This device supports and aligns the fiber allowing for a precise coupling of one fiber to another when the connection is made. In the case of a single fiber connector, the ferrule is a cylindrically shaped structure, often ceramic, which holds the fiber in its center with the aid of a cured epoxy resin. The end of the fiber and the ferrule are polished to create an optically smooth, large planar surface with the optical fiber aligned as close as possible to the center of the device. When two keyed ferrules are aligned end to end through a mechanical connector, optical coupling takes place between the two fibers allowing the optical connection to be made. Often, the joining ferrule surfaces are not orthogonal in order to reduce unwanted reflection.
Multiple fiber connectors employ a ferrule that is generally rectangular in shape with grooves or holes allowing for precise alignment of a plurality of fibers. These fibers are supported in a single, parallel array, separated by 250 microns on center.
It is desirable to interface optical fibers and optical fiber arrays with a printed circuit board so that they lay along the surface of the board and then bend into the board so that they form a right angle with the surface of the board. Optical fiber as used in standard telecommunications and other applications is limited by its physical structure in its ability to make a right angle transition. Physically bending the fiber at such a right angle may cause strain that leads to fractures and structural imbalances in the fiber material. Repeated flexing of fibers bent in such a way exacerbates the failure risk.
Thus, what is needed is a way to make an abrupt right angle bend of an optical fiber or fiber array into a printed circuit board in a manner that is stable and prevents repeated flexing.